Hermetically sealed insulating assembly

ABSTRACT

First and second spaced members are hermetically sealed by a partially amorphous and partially crystalline insulating material. The insulating material is non-hygroscopic and is able to withstand forces of about 26,000 psi at about 700° F. It may provide resistances of at least 10,000 megohms even when subjected to 500 volts AC or DC and to steam at about 212° F. for three (3) days. A second insulating layer may be fused to the first insulating layer with essentially the same properties and composition as the first layer. However, the second layer may be more crystalline than the first layer to provide a mechanical and chemical barrier. The insulating materials may be formed from the oxides of lead, zinc, aluminum, silicon, cerium, lanthanum, cobalt, sodium, zirconium, bismuth and molybdenum. The oxides of lead, silicon, bismuth and sodium may be glass formers. The oxides of cerium, lanthanum and zirconium may form crystals. A mixture of the oxides may be heated to at least 2000° F. for several hours and quenched in water to form first beads. These beads may be disposed between the first and second members. The assembly may then be heated for a limited time at about 1900° F. and then quenched. The second insulating material may be formed into beads as described above. These beads may be disposed to abut the first beads. The insulating materials may then be fused by heating them to the elevated temperature for the limited time as discussed above.

This is a continuation of application Ser. No. 111,787, filed Jan. 9,1980, now abandoned.

This invention relates to a hermetically sealed assembly which hasproperties of withstanding considerable forces and providing highelectrical resistances even when subjected to extreme adverseconditions. The invention is particularly adapted to be used in oilwells to produce a hermetic seal for protecting expensive electricalequipment when such electrical equipment is disposed in the well. theinvention also relates to the chemical composition of the insulatingmaterial which constitutes one of the features of the invention andwhich is included in the assembly to produce the hermetic seal. Theinvention further relates to a method of producing such insulatingmaterial and of producing the hermetic seal.

In previous years, it has been relatively easy to drill for oil inreserves below the ground and to withdraw such oil to ground level.However, as oil has become depleted, it has become necessary to drillfor oil at increasing depths below the ground. Furthermore, it hasbecome increasingly difficult to withdraw such oil from its positions ofdeposit and to raise such oil to ground level. This has resulted in partbecause of the increased depth of the oil, the increased viscosity ofthe oil and the disposition of the oil in the surrounding soil.

In order to withdraw the oil efficiently, it has been necessary toprovide instruments of increased sophistication for use with the oilwell equipment to determine various parameters which control theoperation of the oil well equipment. In order for such instruments tooperate satisfactorily, the instruments have had to be shielded so thatthey are not subjected to excessive mechanical or electrical forces orother parameters of an extreme nature. As a result, the instruments havebeen disposed in log heads which have been shielded from the oil wellequipment so that the instruments can provide reliable and sensitivemeasurements of different parameters. Such shielding has been providedby insulating materials which have been included in the log head toshield the instruments from the forces and other parameters existing onan adverse basis on one side of the log head.

The adverse conditions to be shielded from the measuring equipments maybe seen from the following specifications. The oil well equipments areoften subjected to pressures as high as twenty six thousand (26,000)pounds per square inch. The problems relating to such forces arecompounded because the temperatures in the oil well may be as high as700° F. As will be seen, it is quite difficult to provide materialswhich will withstand forces as high as twenty six thousand (26,000)pounds per square inch at temperatures as high as 700° F. Furthermore,in order to provide a proper shielding of the measuring equipment, thematerials providing the shielding should provide electrical resistancesas high as ten thousand (10,000) megohms even when subjected topotentials as high as five hundred (500) volts AC or DC. This highelectrical resistance should exist even when the shielding materials aresubjected to such adverse conditions as steam at 212° F. for extendedperiods of time such as three (3) days. In other words, the materialsshould be non-hygroscopic.

Various insulating materials have been provided until now with limitedsuccess in achieving the parameters discussed in the previous paragraph.However, the materials have not been successful because they have notbeen able to withstand the mechanical forces described above or providethe electrical resistances described above, at least at the elevatedtemperatures and for the extended periods of time described above. Whenthe materials have been unable to provide such parameters, the oil wellequipment has had to be withdrawn from the well and new materials havehad to be substituted. This has substantially reduced the time ofoperating such equipment and has also considerably increased the cost ofsuch operation. As a result, the limitations in such shielding materialshave materially affected the economics of recovering oil from positionsbelow the ground.

Various attempts have been made throughout a long number of years toprovide assemblies which will overcome the above disadvantages. Suchattempts have been far from successful. Oil well equipments have beenable to be operated only for limited periods of time withoutsubstituting new shielding material because the shielding materials havefailed after only a limited period of use. The attempts to providesatisfactory shielding materials have been unsuccessful even as the costof oil has escalated and the importance of oil from economic andpolitical standpoints has increased.

This invention relates to apparatus which has particular utility in oilwell equipment but also has utility in a number of other fields whereextreme conditions of temperature and mechanical and electrical forcesmay occur. The invention also relates to a particular insulatingmaterial which is included in such apparatus to provide a hermetic seal.This material has partially crystalline and partially amorphouscharacteristics. The invention further relates to a method of producingsuch insulating material and also to a method of producing articleswhich include the insulating material to provide a hermetic seal. Theinvention further relates to apparatus which includes two fused layersof insulating material, with one layer providing a hermetic seal and theother providing an enhanced barrier against the passage of mechanicaland electrical forces.

In one embodiment of the invention, a first member and a second memberspaced from each other are hermetically sealed by the insulatingmaterial included in this invention. The insulating material may bepartially amorphous and partially crystalline. The insulating materialmay have properties of providing an exceptionally high electricalresistance and may be non-hygroscopic and may be able to withstand veryhigh forces. For example, the material may be able to withstand forcesin the order of twenty six thousand (26,000) pounds per square inch evenat temperatures in the order of 700° F. The material may provideresistances of at least ten thousand (10,000) megohms even whensubjected to potentials as high as 500 volts AC or DC. The material mayeven provide such resistances even after being subjected to steam atapproximately 212° F. in a confined space for a period as long as three(3) days and then being blow dried with dry nitrogen for approximatelythirty (30) seconds.

A second layer of insulating material may be fused to the first layer ofinsulating material. The second layer of insulating material may haveproperties approaching those of the first layer. However, the secondlayer of insulating material may be more crystalline than the firstlayer. This facilitates the operation of the second layer of insulatingmaterial in providing a mechanical, chemical and electrical barrier. Thesecond layer of insulating material may actually have substantially thesame chemicals as the first layer but in different proportions than thefirst layer.

The insulating materials may be formed from the oxides of lead(preferably red lead), zinc, aluminum (preferably calcined), silicon,cerium, lanthanum, cobalt, sodium, zirconium, bismuth and molybdenum.The oxides of lead, silicon, bismuth and sodium may be glass formers.The oxides of cerium, lanthanum, zinc and zirconium may form crystals.Such oxides as those of cobalt and molybdenum are especially desirablewhen the members to be hermetically sealed are made from an alloy suchas that designated as "Inconel", which has a composition including suchmetals as nickel, cobalt, iron, vanadium and chromium.

The insulating material may be formed and may be fused to the first andsecond members by a novel method. A mixture of the oxides specifiedabove may be provided and heated to a temperature of at least 2000° F.for a relatively extended period such as several hours, a period such asapproximately three (3) hours being preferable. The mixture may be thenguenched in water and particles of the quenched mixture of differentsizes may be formed into beads.

The beads may then be disposed in the space between the first and secondspaced members. The assembly may then be heated for a limited period oftime, such as a period of approximately twenty (20) minutes to forty(40) minutes, at an elevated temperature in the order of 1900° F. Theassembly may subsequently be quenched, preferably in air at ambient roomtemperatures.

When the second insulating material is fused to the first insulatingmaterial, the second insulating material may initially be formed intobeads in the manner described above. The beads of the first insulatingmaterial may then be disposed in one layer and the beads of the secondinsulating material may be disposed in a second layer on the firstlayer. The two layers may then be fused at the elevated temperature of1900° F. for the limited period of time.

In the drawings:

FIG. 1 is a schematic view of an oil well, oil well equipment in thewell and instruments for determining parameters in the well and fortesting the operation of the oil well equipment;

FIG. 2 is a sectional view of apparatus constituting one embodiment ofthe invention for isolating the testing instruments from the oil wellequipment; and

FIG. 3 is a sectional view of apparatus constituting a second embodimentof the invention for isolating the testing instruments from the oil wellequipment.

In one embodiment of the invention, apparatus generally indicated at 10is provided for use in oil wells. The apparatus includes a log head 12having a generally U-shaped configuration. This U-shaped configurationis defined by a bottom leg 14 and a pair of arms 16 and 18 extendingupwardly from the outer ends of the leg 14 to define a sheltered area20. An aperture 22 is provided in the leg 14 at an intermediate positionalong the length of the leg. A rod 24 extends through the aperture 22 inspaced relationship to the walls of the leg 14. Insulating materialgenerally indicated at 26 and constituting one of the features of theinvention hermetically seals the rod 24 and the log head 12.

The insulating material 26 is hermetically sealed to a ferrule 27 whichextends through the aperture 22 and which has a collar 29 disposedagainst the bottom leg 14 of the log head 12. The bottom of the ferrule27 is threaded to receive a threaded nut 31. The ferrule 27 and the nut31 enclose suitable insulating material 33.

The apparatus 10 is constructed to be lowered into an oil well,generally indicated at 40, to the depth at which oil is recovered fromthe well. The area below the log head 12 experiences conditions of anextreme nature. For example, the rod 24 may be subjected to forces ashigh as twenty six thousand (26,000) pounds per square inch at positionsbelow the log head 12. Furthermore, such forces may be imposed attemperatures as high as 700° F. The area below the log head 12 may alsobe subjected to live steam in confined quarters at 212° F. for extendedperiods of times such as three (3) days or even longer.

Electrical instruments 28 may be disposed in the sheltered area 20defined by the log head 12. Such equipment may be provided to measurevarious parameters relating to conditions within the oil well andfurther relating to the operation of the oil well equipment. Suchinstruments 28 are disposed within the sheltered area 20 so that thearea will be isolated from the extreme conditions imposed upon the oilwell equipment at positions below the log head 12. By isolating suchinstruments 28 from such extreme conditions, the instruments are able tooperate in a sensitive and reliable manner. Furthermore, the instrumentscan be designed to operate under ambient conditions which are relativelynormal. Such design of the instruments facilitates the sensitive andreliable operation of the equipment and minimizes their cost.

The insulating material 26 has characteristics for hermetically sealingthe rod 24 and the log head 12 in such a manner that the extremeconditions below the log head are isolated from the sheltered areawithin the log head. For example, the insulating material 26 is able towithstand forces as high as twenty six thousand (26,000) pounds persquare inch. Furthermore, the insulating material is able to withstandsuch forces even at temperatures as high as 700° F. The insulatingmaterial also provides electrical resistances as high as ten thousand(10,000) megohms even when subjected to potentials as high as fivehundred (500) volts DC or AC. The insulating material 26 is alsonon-hygroscopic. For example, the insulating material is still able toprovide electrical resistances as high as ten thousand (10,000) megohmseven after being subjected to live steam at a temperature of 212° F. ina confined space for a period as long as three (3) days and thereafterbeing blow dried for a period as short as thirty (30) seconds.

The rod 24, the ferrule 27 and the log head 12 are preferably made fromthe same or similar materials. This material is preferably an alloy ofnickel, cobalt, iron, vanadium and chromium designated by the trademark"INCONEL". For example, the material commonly designated in industry as"INCONEL 750" may be used. One source of such material may be CastleMetals of Los Angeles, Calif. When such materials are used, thecombination of the rod 24, the log head 12 and the insulating material26 provide no absorption of moisture and a completely stable systemunder the adverse conditions discussed in the previous paragraph. Thiscauses the equipment 28 to be completely isolated within the log head 12from the extreme conditions encountered outside of the log head.

The stable conditions encountered by the combination of the rod 24, thelog head 12 and the insulating material 26 are contrary to all knownglasses or amorphous compounds which may be similar to glasses. Forexample, all of these glasses and amorphous compounds are at leastslightly soluble in water. Furthermore, none of these glasses has theability to withstand the forces occurring at times in oil wells,particularly at the elevated temperatures encountered. These glasses andamorphous compounds are accordingly unsatisfactory for use in theextreme conditions described above.

The insulating material 26 may be formed from the following materials inthe following relative amounts by weight:

    ______________________________________                                                            Relative                                                  Material            Amount by Weight                                          ______________________________________                                        Lead oxide (preferably red lead)                                                                  355                                                       Zinc oxide          40                                                        Alumina (preferably calcined)                                                                     20                                                        Silicon dioxide     300                                                       Cerium oxide        10                                                        Lanthanum oxide     30                                                        Cobalt oxide        15                                                        Sodium antimonate   80                                                        Zinc zirconium silicate                                                                           30                                                        Bismuth trioxide    100                                                       Molybdenum trioxide 30       (but as low                                                                   as 0.5% by                                                                    weight)                                          ______________________________________                                    

Oxides selected from a group consisting of the oxides of chromium,nickel and manganese may be substituted for the oxide of cobalt. Oxidesselected from a group consisting of the oxides of lithium and potassiummay be substituted for the oxide of sodium. The oxide of lanthanum maybe substituted for the oxide of cerium. A material such as zinczirconium silicate may be substituted for the oxide of zinc. However,all of such substitutions may cause the properties of the resultantinsulating material to deteriorate slightly from the properties of thematerial obtained from the mixture specified above.

The insulating material forming a part of this invention is produced bya novel method. The different materials are initially weighted andmilled and dried in a dry ball mill for an extended period of time suchas approximately three (3) hours. The materials may then be placed in amullite crucible preheated to a suitable temperature such asapproximately 2200° F. The mixture may be heated in the preheatedcrucible at a suitable temperature such as a temperature ofapproximately 2200° F. for an extended period of time such asapproximately six (6) hours. The mixture may thereafter be air cooled toa suitable temperature such as approximately 1000° F. The material maysubsequently be heated in the mullite crucible to an elevatedtemperature such as approximately 2000° F. for an extended period suchas approximately five (5) hours.

The smelted mixture may thereafter be fritted in deionized water andground into particles in a suitable pulverizer which isnon-contaminated. The particles may then be mixed with a suitab;e binderand may be pressed into beads which are then sintered at a suitabletemperature such as approximately 1400° F. A suitable binder may bepolyethylene glycol (marketed under the name "carbowax") or an animalfat. The beads may subsequently be disposed in the space between the rod24 and the ferrule 27.

To produce the hermetic seal between the rod 24, the ferrule 27 and theinsulating material 26, the assembly may be heated for a limited periodof time at a suitable elevated temperature. For example, the assemblymay be may be heated at a temperature of approximately 1900° F. for alimited period such as approximately twenty (20) to forty (40) minutes.This causes the insulating material 26 to become fused to the rod 24 andthe ferrule 27.

Preferably, the heating of the assembly at the elevated temperature forthe limited period of time is provided in an oxygen-rich furnace. Byproviding for the heating of the assembly in an oxygen-rich atmosphere,the formation of oxygen bonds between the insulating material 26 and therod 24 and between the insulating material 26 and the ferrule 27 isfacilitated. Conversely, the formation of carbides with the iron in the"INCONEL" alloy is inhibited.

The assembly is subsequently cooled rapidly as by quenching the assemblyat ambient room temperature. This quenching creates a strong compressionof the insulating material around the periphery of the insulatingmaterial. However, the core of the insulating material 26 has a reducedcompression relative to that at the periphery of the insulatingmaterial. The formation of a hermetic seal with the insulating material26 under compression at the boundaries with the rod 24 and the ferrule27 insures that the hermetic seal will be maintained even when theassembly encounters wide variations in conditions.

In the insulating material 26, the oxides of lead, silicon, bismuth andsodium constitute glass formers. The oxides of cerium, lanthanum, zincand zirconium produce crystallites. These crystallites have differentsizes and shapes to enhance the ability of the insulating material towithstand different operating conditions. The amount of crystallites inthe material may be in the order of eighty five percent (85%) to ninetypercent (90%) and the remainder of the material may be amorphous. Theamorphous portion may be dispersed somewhat uniformly throughout theinsulating material.

The oxides of zinc and aluminum tend to increase the viscosity of theinsulating material 26. The oxide of aluminum also increases the meltingtemperature of the insulating material. In addition to producingcrystallites, the oxide of cerium prevents the oxide of lanthanum fromcrystallizing too quickly or from crystallizing irregularly. As aresult, the oxide of cerium is instrumental in providing homogeneity inthe insulating material. The oxide of cobalt and the oxide of molybdenumenhance the bond of the insulating material to certain elements such asnickel, vanadium and chromium when the rod 24 and the ferrule 27 aremade from a suitable material such as an "INCONEL" alloy. The oxide ofbismuth tends to promote high surface resistivity, thereby increasingthe electrical resistance of the material. The oxide of bismuth alsotends to prevent lead from leaching out of the material.

Layers of insulating material 30 and 32 may be fused to the insulatingmaterial 26 at opposite ends of the insulating material 26. The layers30 and 32 may be provided with properties compatible with the propertiesof the insulating material 26. Preferably, the layers 30 and 32 haveproperties which correspond substantially to the properties of the layer26. Even more preferably, the layers 30 and 32 have compositionscorresponding substantially to the composition of the layer 26. Theinsulating layers 30 and 32 are not hermetically sealed to the rod 24and the ferrule 27.

The insulating materials 30 and 32 provide certain advantages. Thematerials are substantially completely polycrystalline. This causes thematerials to be formed with substantially flat surfaces at the endsdisplaced from the material 26. Because of these flat surfaces, othercomponents can be disposed in a flush relationship with the outersurfaces of the layers 30 and 32 to facilitate assembly of differentcomponents in a compact relationship. The insulating layers 30 and 32also provide a mechanical, electrical and chemical barrier. This causesthe insulating materials 26, 30 and 32 to withstand electrical andmechanical forces imposed against the materials and to withstand theeffects of deleterious chemicals passing to the materials.

The preferred composition of the insulating materials 30 and 32 is setforth in the following table:

    ______________________________________                                                              Relative                                                Material              Amount by Weight                                        ______________________________________                                        Oxide of lead (red lead)                                                                            480                                                     Oxide of zinc         10                                                      Oxide of aluminum (preferably calcined)                                                             24                                                      Silicon dioxide       300                                                     Oxide of cerium       10                                                      Oxide of lanthanum    30                                                      Oxide of cobalt       20                                                      Sodium antimonate     140                                                     Zinc zirconium silicate                                                                             31                                                      Bismuth trioxide      40                                                      Molybdenum trioxide   22      (but as low                                                                   as 0.5% by                                                                    weight)                                         ______________________________________                                    

Various substitutions may be made in the different oxides as specifiedabove for the insulating material 26.

As will be seen, the preferred embodiment of the insulating materials 30and 32 corresponds substantially to the preferred embodiment of theinsulating material 26 with certain specific differences. One primarydifference is that the relative amount of sodium antimonate in theinsulating materials 30 and 32 is significantly greater than the amountof sodium antimonate in the insulating material 26. However, therelative amount of bismuth trioxide in the insulating materials 30 and32 is significantly less than the amount of that material in theinsulating material 26. A further significant difference is that theamount of zinc oxide in the insulating materials 30 and 32 isconsiderably less than the amount of zinc oxide in the insulatingmaterial 26.

Furthermore, even though the amounts of cobalt oxide and molybdenumtrioxide in the insulating material 26 and in the insulating materials30 and 32 are relatively low, there is a somewhat significant differencein percentage between the relative amounts of these oxides in theinsulating material 26 and in the insulating materials 30 and 32.However, since the cobalt oxide and the molybdenum trioxide enhance thebond to nickel, the net effect of the oxide of cobalt and the trioxideof molybdenum in the insulating material 26 and the insulating materials30 and 32 may be approximately the same. This results from the fact thatthe amount of cobalt oxide in the insulating material 26 is less thanthat in the materials 30 and 32 but the amount of molybdenum trioxide inthe material 26 is greater than in the materials 30 and 32.

The mixture forming the insulating materials 30 and 32 is smelted at atemperature of approximately 2000° F. for an extended period such as aperiod of approximately four (4) to six (6) hours. The material is thenformed into a bead in the manner described above. These beads are addedas layers to the beads forming the insulating material 26 and theassembly is then fused at a particular temperature such as 1900° F. fora limited period of time such as approximately twenty (20) to forty (40)minutes.

Although this application has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

I claim:
 1. In combination,a first member, a second member disposed inspaced relationship to the first member, a first insulating materialdisposed between the first and second members in hermetically sealedrelationship to these members and having a partially crystalline andpartially amorphous composition, and a second insulating materialdisposed between the first and second members in fused relationship tothe first insulating material and having a more crystalline compositionthan the first insulating material and providing a mechanical andchemical barrier, the chemicals constituting the first insulatingmaterial being the same as the chemicals constituting the secondinsulating material, the first and second insulating materials beingnon-hygroscopic.
 2. The combination set forth in claim 1 whereinthefirst and second insulating materials have characteristics of preventingthe passage of gases and have electrical resistances in the order ofthousands of megohms when subjected to hundreds of direct volts oralternating volts.
 3. The combination set forth in claim 1 whereinthefirst and second members are made from an alloy of nickel, chromium andiron.
 4. The combination set forth in claim 1, including,the secondmember being capable of being subjected to pressures in the order oftens of thousands of pounds per square inch on one surface and torelatively little pressure on a second surface displaced from the firstsurface and the first and second insulating materials being capable ofwithstanding this difference in pressure.
 5. The combination set forthin claim 1, whereinthe second insulating material is substantiallycompletely polycrystalline and has a substantially flat surface at theend opposite the first insulating material.
 6. The combination set forthin claim 5, whereinthe first and second insulating materials include theoxide of bismuth and the first insulating material has considerably morebismuth oxide than the second insulating material.
 7. The combinationset forth in claim 6 whereinthe first and second insulating materialsinclude sodium antimonate and the second insulating material has moresodium antimonate than the first insulating material.
 8. The combinationset forth in claim 7 whereinthe first and second insulating materialsinclude the oxides of lead, zinc, aluminum, silicon, cerium, lanthanum,cobalt, sodium, zirconium and molybdenum.
 9. The combination set forthin claim 1, including,a third insulating material disposed between thefirst and second members on the opposite side of the first insulatingmaterial from the second insulating material and fused to the firstinsulating material and having a more crystalline composition than thefirst insulating material and providing a mechanical and chemicalbarrier and formed from essentially the same chemicals as the firstinsulating material.
 10. The combination set forth in claim 9 whereinthefirst, second and third insulating materials include the oxides of lead,silicon and bismuth and also include sodium antimonate.
 11. Incombination,a first member, a second member disposed in spacedrelationship to the first member and having a first surface forreceiving pressures to approximately twenty-six thousand pounds persquare inch and having a second surface for receiving minimal pounds persquare inch, the second member being constructed to withstand thepressures to approximately twenty-six thousand pounds per square inchbetween its first and second surfaces, a ceramic insulating materialdisposed between the first and second members in hermetically sealedrelationship to the first and second members and having partiallyamorphous and partially polycrystalline properties, the ceramicinsulating material withstanding pressures to approximately twenty-sixthousand pounds per square inch while retaining the hermetic seal withthe first and second members, the ceramic insulating material havingelectrical resistances in the order of ten thousand megohms even afterbeing subjected to live steam for extended periods of time, the ceramicinsulating material being non-hygroscopic and providing an electricalinsulation of approximately ten thousand megohms even after beingsubjected to an exposure of live steam for approximately three (3) daysat a temperature of approximately 212° F. in a confined space and beingblow dried for approximately thirty (30) seconds with dry nitrogen, theceramic insulating material including the oxides of zinc, cerium andlanthanum and sodium antimonate.
 12. In combination,a first member, asecond member disposed in spaced relationship to the first member andhaving a first surface for receiving pressures to approximatelytwenty-six thousand pounds per square inch and having a second surfacefor receiving minimal pounds per square inch, the second member beingconstructed to withstand the pressures to approximately twenty-sixthousand pounds per square inch between its first and second surfaces, aceramic insulating material disposed between the first and secondmembers in hermetically sealed relationship to the first and secondmembers and having partially amorphous and partially polycrystallineproperties, the ceramic insulating material withstanding pressures toapproximately twenty-six thousand pounds per square inch while retainingthe hermetic seal with the first and second members, the ceramicinsulating material having electrical resistances in the order of tenthousand megohms even after being subjected to live steam for extendedperiods of time, the ceramic insulating material including the oxides oflead, zinc, aluminum, silicon, cerium, lanthanum, cobalt, sodium,zirconium and bismuth and also including sodium antimonate.
 13. Incombination,a first member, a second member disposed in spacedrelationship to the first member and having a first surface forreceiving pressures to approximately twenty-six thousand pounds persquare inch and having a second surface for receiving minimal pounds persquare inch, the second member being constructed to withstand thepressures to approximately twenty-six thousand pounds per square inchbetween its first and second surfaces, a ceramic insulating materialdisposed between the first and second members in hermetically sealedrelationship to the first and second members and having partiallyamorphous and partially polycrystalline properties, the ceramicinsulating material withstanding pressures to approximately twenty-sixthousand pounds per square inch while retaining the hermetic seal withthe first and second members, the ceramic insulating material having thefollowing composition:

    ______________________________________                                        Material       Relative Amount By Weight                                      ______________________________________                                        Lead oxide     455                                                            Zinc oxide     40                                                             Alumina        20                                                             Silicon dioxide                                                                              300                                                            Cerium oxide   10                                                             Lanthanum oxide                                                                              30                                                             Cobalt oxide   15                                                             Sodium antimonate                                                                            80                                                             Zinc zirconium silicate                                                                      30                                                             Bismuth trioxide                                                                             100                                                            Molybdenum trioxide                                                                          30                                                             ______________________________________                                    


14. The combination set forth in claim 13, including,a second ceramicinsulating material disposed between the first and second members infused relationship to the first ceramic insulating material and formedfrom the same chemicals as the first ceramic insulating material memberand provided with more crystalline properties than the first ceramicinsulating material and providing a mechanical and chemical barrier, thesecond ceramic insulating material having the following composition:

    ______________________________________                                        Chemical       Relative Amount By Weight                                      ______________________________________                                        Lead oxide     480                                                            Zinc oxide     10                                                             Alumina        24                                                             Silicon dioxide                                                                              300                                                            Cerium oxide   10                                                             Lanthanum oxide                                                                              30                                                             Cobalt oxide   20                                                             Sodium antimonate                                                                            140                                                            Zinc zirconium silicate                                                                      31                                                             Bismuth trioxide                                                                             40                                                             Molybdenum trioxide                                                                          22                                                             ______________________________________                                    